A resistance bridge is a device for comparing resistors by measuring and calculating a ratio between the resistors. For instance, a resistance bridge may be used to determine a resistance value of a first resistor that is electrically coupled to a second resistor. The resistance bridge measures electrical parameters of the two resistors, and, based on the electrical measurements, a microprocessor coupled to the resistance bridge calculates a resistance ratio of the two resistors. Resistance bridges may be used in a wide variety of applications that may use resistance measurements, such as thermometers, resistor calibrators, multimeters and the like. In general, resistance bridge measurement circuits provide high accuracy measurements. However, the accuracy of any circuit depends on the stability of the electrical components within the circuit.
To verify the accuracy of a resistance bridge measurement circuit a test or calibration may be performed. In some cases, a linearity test may be performed to test the accuracy of the range at which the resistance bridge can compare resistors. More particularly, a linearity test may verify the ability of a measurement circuit to accurately measure an output parameter, such as a voltage across two resistors, across a range of input values. In general, during a linearity test a variety of measurements may be performed and compared to expected results.
In the prior art, external resistors are coupled to a resistance bridge to perform a linearity test. In general, it may be difficult to perform a linearity test because a user typically may be required to make complex electrical calculations and/or connect a variety of external resistors to the resistance bridge. Thus, linearity tests require a substantial amount of time and technical expertise from the user. Furthermore, during a linearity test it is important that the stability of the electrical components be carefully controlled during testing. For instance, it may be difficult to precisely know the resistances of the resistors during testing. Additionally, the greater the number of measurements made, the more accurate the test. This all, however, adds to the complexity of conducting a linearity test because more calculations may be required and more resistors may be required to be connected and/or disconnected to the resistance bridge measurement circuit. Therefore, calibrating or testing a resistance bridge measurement circuit requires a great deal of time and expertise from the user.
There is, therefore, a need for a resistance bridge measurement circuit verification or calibration test that provides consistent and accurate results that are quickly and easily implemented by a user.